Electronic internal combustion engine ignition spark vacuum and speed advance system with ignition dwell time directly proportional to engine speed

ABSTRACT

A first and a second series of phase displaced leading and trailing electrical signal wave forms of a potential level proportional to engine speed are generated in timed relationship with the engine, the potential level of the first series being greater than that of the second series over the engine speed range, and an absolute pressure transducer produces an engine manifold absolute pressure electrical signal of a potential level proportonal to engine manifold absolute pressure. The engine manifold absolute pressure signal and the leading and trailing electrical wave form series are compared by respective comparator circuits. While the potential level of each of the leading electrical signal wave forms is equal to or greater than that of the engine manifold absolute pressure signal, the corresponding comparator circuit produces an output ignition dwell signal and when the potential level of each of the trailing electrical signal wave forms has increased to that of the engine manifold absolute pressure signal, the corresponding comparator circuit produces an output ignition signal. An electronic ignition circuit is responsive to each of the ignition dwell signals for completing and to each of the ignition signals for interrupting, respectively, an energizing circuit for the primary winding of an associated ignition coil.

This invention is directed to an improved internal combustion engineignition spark manifold absolute pressure and speed advance system and,more specifically, to an improved system for electronically providinginternal combustion engine ignition spark manifold absolute pressure andspeed advance and an ignition dwell time which increases with enginespeed.

In prior art internal combustion engine ignition systems, the ignitionspark vacuum advance was produced by a vacuum motor, in communicationwith a port in the engine intake manifold, which revolves the ignitiondistributor breaker plate in a direction to advance ignition sparktiming as the intake manifold vacuum became greater and the ignitionspark speed advance is produced by weights rotated by the ignitiondistributor shaft which are mechanically linked with the ignitiondistributor breaker plate to revolve the breaker plate in a direction toincrease ignition spark advance with increases of engine speed and viceversa. The prior ignition systems, therefore, are subject to errors inthat the mechanical linkage of all mass produced ignition spark vacuumand speed advance systems can not be manufactured identical to eachother and the problem of wear over a period of time that the engine isoperated introduces errors into both the vacuum and speed advancelinkages. Furthermore, the vacuum advance is responsive to intakemanifold vacuum, consequently, the ignition spark vacuum advance isconsiderably different between sea level atmospheric pressures andatmospheric pressures at higher altitudes. Therefore, a system whichprovides internal combustion engine ignition spark manifold absolutepressure and speed advance electronically to eliminate the undesirablefeatures of the prior art systems, is desirable.

It is, therefore, an object of this invention to provide an improvedinternal combustion engine ignition spark manifold absolute pressure andspeed advance system.

It is another object of this invention to provide an improved internalcombustion engine ignition spark manifold absolute pressure and speedadvance system wherein the manifold absolute pressure and speed advanceand variable ignition dwell time is produced electronically in responseto electrical signals proportional to engine manifold absolute pressureand engine speed.

In accordance with this invention, an improved electronic internalcombustion engine ignition spark manifold absolute pressure and speedadvance system with variable ignition dwell time is provided whereinseparate comparator circuits produce, respectively, an output ignitiondwell signal when the potential level of each of a series of leadingpotential wave forms, produced in timed relationship with the engine, isof a magnitude equal to or greater than an engine manifold absolutepressure signal produced by an absolute pressure transducer and anoutput ignition signal when the potential level of each of a series oftrailing potential wave forms, produced in timed relationship with theengine of a potential level greater than and phase displaced from theleading signal wave forms, rises to that of the engine manifold absolutepressure signal and an electronic ignition circuit in responsive to thedwell and ignition signals for completing and interrupting,respectively, an energizing circuit for the primary winding of anassociated ignition coil.

For a better understanding of the present invention, together withadditional objects, advantages and features thereof, reference is madeto the following description and accompanying drawing in which:

FIG. 1 is a schematic diagram of the electronic internal combustionengine ignition spark manifold absolute pressure and speed advancesystem of this invention; and

FIGS. 2, 3, and 4 a-c are respective sets of curves useful inunderstanding the operation of the circuit of FIG. 1.

As point of reference or ground potential is the same point electricallythroughout the system, it has been represented in FIG. 1 by the acceptedschematic symbol and referenced by the numeral 5.

Referring to FIG. 1, the electronic internal combustion engine ignitionspark manifold absolute pressure and speed advance system of thisinvention is set forth in schematic form in combination with an internalcombustion engine 6 and an ignition coil 7 having a primary winding 8and a secondary winding 9. The electrical operating potential may besupplied by a conventional storage battery 4 or any other direct currentpotential source well known in the art.

To produce, in timed relationship with engine 6, two series of phasedisplaced leading and trailing electrical signal wave forms of apotential level proportional to engine speed with the potential level ofthe trailing electrical signal wave forms being greater than thepotential level of the leading electrical signal wave forms over theengine speed range, a magnetic pickup arrangement, generally shown at10, is provided. Electrical pickup arrangement 10 includes two pickupcoils 11 and 12, a rotating member 13 and two permanent magnets 14 and15 mounted upon and rotated with rotating member 13. Rotating member 13is rotated by engine 6 and may be a drum mounted upon the enginecrankshaft, or it may be mounted upon the engine flywheel, or it may bemounted upon the engine dynamic balancer or any other vehicle part whichis rotated at a speed equal to or proportional to vehicle engine speed.It is only necessary that the permanent magnets 14 and 15 be passed inclose enough proximity to pickup coils 11 and 12 that the magnetic fluxproduced thereby link pickup coils 11 and 12 in a manner well known inthe magnetic pickup art. Without intention or inference of a limitationthereto, it will be assumed for purposes of this specification thatinternal combustion engine 6 rotates rotating member 13 in a clockwisedirection, as viewing FIG. 1, that permanent magnets 14 and 15 aremounted 180 mechanical degrees apart and are magnetized in a radialdirection with the north poles thereof facing outwardly from the centerof rotating member 13. It is to be specifically understood thatpermanent magnets 14 and 15 may be radially magnetized in the oppositedirection and that rotating member 13 may be rotated in acounterclockwise direction without departing from the spirit of theinvention. To provide a phase displacement between the series of leadingelectrical signal wave forms induced in pickup coil 11 and the series oftrailing, higher potential level electrical signal wave forms induced inpickup coil 12 as rotating member 13 is rotated in a clockwisedirection, pickup coils 11 and 12 may be displaced from each other by apredetermined number of mechanical degrees. For purposes of thisspecification and without intention or inference of a limitationthereto, it will be assumed that pickup coils 11 and 12 are displacedfrom each other twenty engine crankshaft degrees, as indicated by angleA in FIG. 1. With this arrangement, each of the leading electricalsignal wave forms of the series induced in pickup coil 11 is phasedisplaced from and leads each of the corresponding higher potentiallevel trailing electrical signal wave forms of the series induced inpickup coil 12 by twenty engine crankshaft degrees. Should rotatingmember 13 be rotated by engine 6 in a counterclockwise direction, theseries of leading electrical signal wave forms would be induced inpickup coil 12 and the series of higher potential level trailingelectrical signal wave forms would be induced in pickup coil 11. Withrotating permanent magnets 14 and 15 passing by and in magnetic linkingarrangement with pickup coils 11 and 12, the output electrical signalwave form from each coil would be of the form illustrated in FIG. 2wherein the output electrical signal wave form of pickup coil 11 isidentified by the reference numeral 11W and the output electrical signalwave form of pickup coil 12 is identified by the reference numeral 12W.By placing diodes 21 and 22 across respective pickup coils 11 and 12,the output of pickup coil 11 will be a series of leading electricalsignal wave forms and the output of pickup coil 12 will be a series ofphase displaced trailing electrical signal wave forms separated by anumber of engine crankshaft degrees equal to angle A, as illustrated inFIG. 3. The electrical signal wave forms induced in pickup coils 11 and12 are of an electrical potential proportional to engine speed and coil12 is wound to provide output electrical signal wave forms of apotential level greater than that of the output electrical signal waveforms produced by pickup coil 11. For example, the potential level ofthe output electrical signal wave forms produced by pickup coil 12 maybe of the order of 1.5 to 2.0 times that of the output electrical signalwave forms produced by pickup coil 11 over the engine speed range. Thatis, as the speed of engine 6 increases, the amplitude of the electricalsignal wave forms induced in pickup coils 11 and 12 increase, theamplitude of the wave forms produced in pickup coils 12 being greaterthan that of the wave forms induced in pickup coil 11 at all enginespeeds. The actual number of engine crankshaft degrees represented byeach of the electrical signal wave forms is determined by the geometryof the magnets and pick-up coils in a manner well known in the magneticpickup art. For purposes of this specification and without intention orinference of a limitation thereto, it will be assumed that each of theelectrical signal wave forms extends over ninety engine crankshaftdegrees.

The magnetic pickup arrangement illustrated in FIG. 1, with permanentmagnets 14 and 15 mounted 180 degrees apart upon rotating member 13, maybe used with four cylinder engines. With this arrangement, the ignitionspark advance will be adjusted every 180 degrees of crankshaft rotation.

To produce an engine manifold absolute pressure electrical signal of apotential level proportional to engine manifold absolute pressure, anabsolute pressure transducer 20 having the input port thereof exposed toengine manifold absolute pressure may be employed. One example of anabsolute pressure transducer suitable for use with this application ismarketed by the National Semiconductor Corporation and is identified asType LX1603A. This pressure transducer produces an electrical outputsignal which is of a potential level proportional to absolute pressureand increases linearly with increases of absolute pressure. In FIG. 1,absolute pressure transducer 20 is indicated in block form and isillustrated as having the intake port thereof in communication withengine intake manifold 3 through line 2. Therefore, as the absolutepressure of the intake manifold 3 of internal combustion engine 6increases, absolute pressure transducer 20 produces an output electricalsignal which increases linearly therewith and is applied across seriesresistors 24 and 25 connected across the output terminal thereof andpoint of reference or ground potential 5.

Junction 26 between series resistors 24 and 25 is connected to the minusinput terminal 2 of respective potential comparator circuits 30 and 40through respective leads 31 and 41. Consequently, resistors 24 and 25are so proportioned that, at maximum absolute pressure, the potentialappearing across junction 26 and point of reference or ground potential5 is of a magnitude compatible with the maximum input signal whichcomparator circuits 30 and 40 will tolerate. The series of phasedisplaced leading electrical signal wave forms produced by pickup coil11 is applied to the plus input terminal 1 of potential comparatorcircuit 30 through lead 32 and the series of trailing electrical signalwave forms produced by pickup coil 12 are applied to the plus inputterminal 1 of potential comparator circuit 40 through lead 42.Comparator circuits 30 and 40 may be any one of the many comparatorcircuits well known in the art. One example of a commercially availablecomparator circuit suitable for use with this application is marketed byNational Semiconductor Corporation and is identified as Type LM2901. Incomparator circuits of this type, output terminal 3 is the uncommittedcollector electrode of the output NPN transistor. Consequently, outputterminal 3 of each of comparator circuits 30 and 40 is connected to thepositive polarity terminal of battery 4 through respective pull-upresistors 33 and 43 and respective leads 34 and 44 and positivepotential bus 18. With comparator circuits of this type, while thepotential level upon the plus input terminal 1 is more positive than thepotential level upon the minus input terminal 2, a positive polaritysignal is present upon output terminal 3 and while the potential levelupon minus input terminal 2 is more positive than the potential levelupon plus input terminal 1, output terminal 3 is near ground potential.

Potential comparator circuit 30 is responsive to the leading electricalsignal wave forms produced by pickup coil 11 and the engine manifoldabsolute pressure signal produced by absolute pressure transducer 20 forproducing an ignition dwell signal while the potential level of each ofthe leading electrical signal wave forms is equal to or greater thanthat of the engine manifold absolute pressure signal. That is, while theleading electrical signal wave form, applied to plus input terminal 1 ofpotential comparator circuit 30, is more positive than that of theengine manifold absolute pressure signal, applied to minus inputterminal 2, the output of potential comparator circuit 30 is of apositive polarity and of a magnitude sufficient to produce base drivecurrent through type NPN transistor 51 of an electronic ignition circuit50. The circuit through which base drive current is supplied to NPNtransistor 51 may be traced from the positive polarity terminal ofbattery 4, through positive polarity bus 18, lead 34, pull-up resistor33, lead 35, current limiting resistor 55, the base-emitter electrodesof NPN transistor 51 and point of reference or ground potential 5 to thenegative polarity terminal of battery 4. While base drive current issupplied to NPN transistor 51, while the potential level of the leadingelectrical signal wave form produced by pickup coil 11 is equal to orgreater than that of the engine manifold absolute pressure signal,transistor 51 conducts through the collector-emitter electrodes thereof.As the base electrode of PNP transistor 52 is connected to the junctionbetween series resistors 56 and 57, while transistor 51 is conductivethrough the collector-emitter electrodes, a circuit is establishedthrough which emitter-base current is supplied to transistor 52. Thiscircuit may be traced from the positive polarity terminal of battery 4,through positive potential bus 18, the emitter-base electrodes oftransistor 52, resistor 57, the collector-emitter electrodes oftransistor 51 and point of reference or ground potential 5 to thenegative polarity terminal of battery 4. While this circuit isestablished, transistor 52 conducts through the emitter-collectorelectrodes thereof to produce a potential drop across collector resistor58. The potential drop across resistor 58 is of a sufficient magnitudeto produce base-emitter drive current through NPN switching transistor53, the base electrode of which is connected to the junction between thecollector electrode of transistor 52 and resistor 58. The circuitthrough which base drive current is supplied to switching transistor 53may be traced from the positive polarity terminal of battery 4, throughpositive polarity bus 18, the emitter-collector electrodes of transistor52, the base-emitter electrodes of switching transistor 53, emitterresistor 59, and point of reference or ground potential 5 to thenegative polarity terminal of battery 4. While base-emitter drivecurrent is being supplied to switching transistor 53, this deviceconducts through the collector-emitter electrodes thereof to establishan energizing circuit for primary winding 8 of ignition coil 7 which maybe traced from the positive polarity terminal of battery 4, throughpositive polarity bus 18, primary winding 8 of ignition coil 7, thecollector-emitter electrodes of switching transistor 53, resistor 59 andpoint of reference or ground potential 5 to the negative polarityterminal of battery 4. From this description, it is apparent that thepositive polarity ignition dwell signal produced by potential comparatorcircuit 30 initiates the action of electronic ignition circuit 50 toestablish the energizing circuit for primary winding 8 of ignition coil7.

Potential comparator circuit 40 is responsive to the trailing electricalsignal wave forms produced by pickup coil 12 and the engine manifoldabsolute pressure signal produced by absolute pressure transducer 20 forproducing an ignition signal when the potential level of the trailingelectrical wave forms has increased to that of the engine manifoldabsolute pressure signal. While the potential of the trailing electricalwave forms is of a level less positive than that of the engine manifoldabsolute pressure signal, the output of comparator circuit 40 is nearground potential. When the potential of the trailing electrical signalwave form has increased to a positive potential level equal to that ofthe engine manifold absolute pressure signal, potential comparatorcircuit 40 produces an ignition signal upon output terminal 3 thereofwhich is of a positive polarity and of a magnitude sufficient to producebase-emitter drive current through NPN transistor 54 of electronicignition circuit 50. The circuit through which base drive current issupplied to transistor 54 may be traced from the positive polarityterminal of battery 4, through positive polarity bus 18, lead 44,pull-up resistor 43, lead 45, current limiting resistor 60, thebase-emitter electrodes of NPN transistor 54 and point of reference orground potential 5 to the negative polarity terminal of battery 4. Thisbase drive current produces collector-emitter conduction through NPNtransistor 54 to drain base drive current from NPN transistor 51, acondition which extinguishes transistor 51. With transistor 51extinguished, the circuit, previously described, through whichemitter-base drive current is supplied to transistor 52 is interrupted,consequently, transistor 52 extinguishes. With transistor 52extinguished, the circuit, previously described, through base drivecurrent is supplied to switching transistor 53 is interrupted,consequently, transistor 53 extinguishes to abruptly interrupt theenergizing circuit of primary winding 8 of ignition coil 7. Theresulting collapsing magnetic field induces an ignition potential insecondary winding 9 in a manner well known in the ignition art. The highignition potential induced in secondary winding 9 is directed to theassociated ignition distributor which further directs this potential tothe spark plugs of the engine in the proper sequence as is well known inthe automotive art. From this description, it is apparent that thepositive polarity ignition signal produced by potential comparatorcircuit 40 initiates the action of electronic ignition circuit 50 toabruptly interrupt the energizing circuit for primary winding 8 ofignition coil 7.

In FIGS. 4A, 4B and 4C, one leading electrical signal wave form producedby pickup coil 11 is shown for each of engine speeds N, 2N and 4N, andone higher potential level trailing electrical signal wave form producedby pickup coil 12 is illustrated for each of engine speeds N, 2N and 4Nand are identified by reference characters n', 2N' and 4N'. It may benoted that the curves of the leading electrical signal wave forms leadthe curves of greater potential level trailing electrical signal waveforms by twenty engine crankshaft degrees as pickup coils 11 and 12 aredisplaced from each other by twenty engine crankshaft degrees, angle Aof FIG. 1. In respective FIGS. 4A, 4B and 4C, three different levels ofengine manifold absolute pressure electrical signals produced byabsolute pressure transducer 20 are indicated and are identified byhorizontal lines labeled MAP level 1 in FIG. 4A, MAP level 2 in FIG. 4Band MAP level 3 in FIG. 4C. In FIGS. 4A, 4B and 4C, it will be assumedthat MAP level 3 corresponds to the manifold absolute pressure at whichthe manifold absolute pressure advance is to be minimum and that MAPlevel 1 corresponds to the manifold absolute pressure at which themanifold absolute pressure advance is to be maximum. Voltage clampingcircuitry may be employed to modify the output signal of absolutepressure transducer 20 to prevent the resultant signal from being lessthan MAP level 1 or greater than MAP level 3.

For purposes of illustration, it will be assumed that engine 6 isoperating at a manifold absolute pressure at which absolute pressuretransducer 20 produces an electrical engine manifold absolute pressuresignal of a level equal to MAP level 1, FIG. 4A. At engine speed N, whenthe potential of the leading electrical signal wave form produced bypickup coil 11, curve N, increases to a level equal to that of theengine manifold absolute pressure signal, point D1, and while it is of apotential level greater than the engine manifold absolute pressuresignal, comparator circuit 30 produces an output ignition dwell signalwhich initiates the operation of electronic ignition circuit 50 tocomplete the energizing circuit for primary winding 8 of ignition coil 7in a manner previously explained. That is, the ignition dwell signalinitiates the ignition dwell time period, the period of time duringwhich primary winding 8 is energized. When the potential of the higherpotential level trailing electrical signal wave form produced by pickupcoil 12, curve N', increases to a level equal to that of the enginemanifold absolute pressure signal, point S1, seven engine crankshaftdegrees later, the number of engine crankshaft degrees between points D1and S1, comparator circuit 40 produces an output ignition signal whichinitiates the operation of electronic ignition circuit 50 to abruptlyinterrupt the energizing circuit for primary winding 8 of ignition coil7 in a manner previously explained. From this description, it isapparent that the ignition dwell time is initiated when and maintainedwhile the leading electrical signal wave form potential level is equalto and greater than the engine manifold absolute pressure signal and theignition spark is initiated seven engine crankshaft degrees later whenthe higher potential level trailing electrical signal wave formpotential level has risen to a value equal to the engine manifoldabsolute pressure signal. At engine speed N, therefore, the ignitiondwell time is seven engine crankshaft degrees. At engine speed 2N, theleading and higher potential level trailing electrical signal wave formsincrease to a potential level equal to MAP level 1 at respective pointsD2 and S2. Therefore, ignition dwell time is initiated twenty enginecrankshaft degrees earlier than at engine speed N, the number of enginecrankshaft degrees between points D1 and D2, ignition spark is advanced16 engine crankshaft degrees from that at engine speed N, the number ofengine crankshaft degrees between points S1 and S2, and ignition dwelltime is ten engine crankshaft degrees, the number of engine crankshaftdegrees between points D2 and S2. At engine speed 4N the leading andhigher potential level trailing electrical signal wave forms increase toa potential level equal to MAP level 1 at respective points D3 and S3.Therefore, ignition dwell time is initiated ten engine crankshaftdegrees earlier than at engine speed 2N, the number of engine orcrankshaft degrees between points D2 and D3, ignition spark is advanced5 engine crankshaft degrees from that at engine speed 2N, the number ofengine crankshaft degrees between points S2 and S3, and ignition dwelltime is 15 engine crankshaft degrees, the number of engine crankshaftdegrees between points D3 and S3. With decreasing engine speed, atengine speed 2N, the ignition dwell time is 10 engine crankshaft degreesand ignition spark advance is reduced 5 engine crankshaft degrees fromthat at engine speed 4N and at engine speed N, the ignition dwell timeis 7 engine crankshaft degrees and ignition spark advance is reduced 16engine crankshaft degrees from that at engine speed 2N.

In FIG. 4B, the leading and higher potential level trailing electricalsignal wave forms for engine speeds N, 2N and 4N are set for engine 6operating at a manifold absolute pressure at which absolute pressuretransducer 20 produces an engine manifold absolute pressure signal equalto MAP level 2. At engine speed N, the leading and higher potentiallevel trailing electrical signal wave forms increase to a potentiallevel equal to MAP level 2 at respective points D1 and S1. At enginespeed N, therefore, ignition dwell time is 8 engine crankshaft degrees,the number of engine crankshaft degrees between points D1 and S1. Atengine speed 2N, the leading and higher potential level trailingelectrical signal wave forms increase to a potential level equal to MAPlevel 2 at respective points D2 and S2. Therefore, ignition dwell timeis initiated 18 engine crank-shaft degrees earlier than at engine speedN, the number of engine crankshaft degrees between points D1 and D2,ignition spark is advanced 15 engine crankshaft degrees from that atengine speed N, the number of engine crankshaft degrees between pointsS1 and S2, and ignition dwell time is 12 engine crankshaft degrees, thenumber of engine crankshaft degrees between points D2 and S2. At enginespeed 4N, the leading and higher poential level trailing electricalsignal wave forms increase to a potential level equal to MAP level 2 atrespective points D3 and S3. Therefore, ignition dwell time is initiated14 engine crankshaft degrees earlier than that at engine speed 2N, thenumber of engine crankshaft degrees between points D2 and D3, ignitionspark is advanced 8 engine crankshaft degrees from that at engine speed2N, the number of engine crankshaft degrees between points S2 and S3,and ignition dwell time is 18 engine crankshaft degrees, the number ofengine crankshaft degrees between points D3 and S3. With decreasingengine speed, at engine speed 2N, the ignition dwell time is 12 enginecrankshaft degrees and ignition spark advance is reduced 8 enginecrankshaft degrees from that at engine speed 4N and at engine speed N,ignition dwell time is 8 engine crankshaft degrees and ignition sparkadvance is reduced 15 engine crankshaft degrees from that at enginespeed 2N.

In FIG. 4C, the leading and higher potential level trailing electricalsignal wave forms for engine speeds N, 2N and 4N are set forth forengine 6 operating at a manifold absolute pressure at which absolutepressure transducer 20 produces an engine manifold absolute pressuresignal equal to MAP level 3. At engine speed N, the leading and higherpotential level trailing electrical signal wave forms increase to apotential level equal to MAP level 3 at respective points D1 and S1. Atengine speed N, therefore, ignition dwell time is 9 engine crankshaftdegrees, the number of engine crankshaft degrees between points D1 andS1. At engine speed 2N, the leading and higher potential level trailingelectrical signal wave forms increase to a potential level equal to MAPlevel 3 at respective points D2 and S2. Therefore, ignition dwell timeis initiated 19 engine crankshaft degrees earlier than at engine speedN, the number of engine crankshaft degrees between points D1 and D2,ignition spark is advanced 14 engine crankshaft degrees from that atengine speed N, the number of engine crankshaft degrees between pointsS1 and S2, and ignition dwell time is 15 engine crankshaft degrees, thenumber of engine crankshaft degrees between points D2 and S2. At enginespeed 4N, the leading and higher potential level trailing electricalsignal wave forms increase to a potential level equal to MAP level 3 atrespective points D3 and S3. Therefore, ignition dwell time is initiatedseventeen engine crankshaft degrees earlier than that at engine speed2N, the number of engine crankshaft degrees between points D2 and D3,ignition spark is advanced 11 engine crankshaft degrees from that atengine speed 2N, the number of engine crankshaft degrees between pointsS2 and S3 and ignition dwell time is twenty engine crankshaft degrees,the number of engine crankshaft degrees between points D3 and S3. Withdecreasing engine speed, at engine speed 2N, the ignition dwell time isfifteen engine crankshaft degrees and ignition spark advance is reducedeleven engine crankshaft degrees from that at engine speed 4N and atengine speed N, ignition dwell time is nine engine crankshaft degreesand ignition spark advance is reduced 14 engine crankshaft degrees fromthat at engine speed 2N.

The leading and higher potential level trailing electrical signal waveforms are coordinated with the piston of the reference cylinder ofengine 6 in such a manner that, at the lowest engine speed and highestmanifold absolute pressure, the potential level of the higher potentiallevel trailing electrical signal wave form rises to MAP level 3 at thenumber of engine crankshaft degrees of initial ignition spark advancerequired by engine 6, for example 5 degrees of initial spark advance.The magnetic pickup arrangement 10, therefore, is adjusted relative tothe piston of the reference engine cylinder in such a manner that thepotential level of the leading electrical signal wave form produced bypickup coil 11 at the lowest engine speed N reaches the MAP level 3engine manifold absolute pressure signal potential level, point D1 ofFIG. 4C, fourteen engine crankshaft degrees before the top dead centerposition of the piston of the reference cylinder so that nine enginecrankshaft degrees later, the amount of ignition dwell time at an enginespeed N at MAP level 3, or at 5 engine crankshaft degrees before the topdead center position of the piston of the reference cylinder, thepotential level of the higher potential level trailing electrical signalwave form will have risen to that of the engine signal level of MAPlevel 3, point S1, FIG. 4C.

While a preferred embodiment of the present invention has been shown anddescribed, it will be obvious to those skilled in the art that variousmodifications and substitutions may be made without departing from thespirit of the invention which is to be limited only within the scope ofthe appended claims.

What is claimed is:
 1. An electronic internal combustion engine ignitionspark vacuum and speed advance system comprising in combination with aninternal combustion engine and an ignition coil having a primarywinding:means for producing in timed relationship with said engine afirst and a second series of phase displaced leading and trailingelectrical signal wave forms of a potential level proportional to enginespeed, the potential level of said second series of trailing electricalwave forms being greater than the potential level of said first seriesof leading electrical signal wave forms over the engine speed range;means for producing an engine manifold absolute pressure electricalsignal of a potential level proportional to engine manifold absolutepressure; means responsive to said leading electrical signal wave formsand said engine manifold absolute pressure signal for producing anignition dwell signal while the potential level of each of said leadingelectrical signal wave forms is greater than that of said enginemanifold absolute pressure signal; means responsive to said trailingelectrical signal wave forms and said engine manifold absolute pressuresignal for producing an ignition signal when the potential level of eachof said trailing electrical signal wave forms has increased to that ofsaid engine manifold absolute pressure signal; and circuit meansresponsive to said dwell time and ignition signals for completing andinterrupting, respectively, an energizing circuit for said primarywinding of said ignition coil.
 2. An electronic internal combustionengine ignition spark vacuum and speed advance system comprising incombination with an internal combustion engine and an ignition coilhaving a primary winding:means for producing in timed relationship withsaid engine a first and a second series of phase displaced leading andtrailing electrical signal wave forms of a positive potential levelproportional to engine speed, the potential level of said second seriesof trailing electrical wave forms being greater than the potential levelof said first series of leading electrical signal wave forms over theengine speed range; means for producing an engine manifold absolutepressure electrical signal of a positive potential level proportional toengine manifold absolute pressure; means responsive to said leadingelectrical signal wave forms and said engine manifold absolute pressuresignal for producing an ignition dwell signal while the potential levelof each of said leading electrical signal wave forms is greater thanthat of said engine manifold absolute pressure signal; means responsiveto said trailing electrical signal wave forms and said engine manifoldabsolute pressure signal for producing an ignition signal when thepotential level of each of said trailing electrical signal wave formshas increased to that of said engine manifold absolute pressure signal;and circuit means responsive to said dwell time and ignition signals forcompleting and interrupting, respectively, an energizing circuit forsaid primary winding of said ignition coil.
 3. An electronic internalcombustion engine ignition spark vacuum and speed advance systemcomprising in combination with an internal combustion engine and anignition coil having a primary winding:means for producing in timedrelationship with said engine a first and a second series of phasedisplaced leading and trailing electrical signal wave forms of apositive potential level proportional to engine speed, the potentiallevel of said second series of trailing electrical wave forms beinggreater than the potential level of said first series of leadingelectrical signal wave forms over the engine speed range; means forproducing an engine manifold absolute pressure electrical signal of apositive potential level proportional to engine manifold absolutepressure; a first comparator circuit responsive to said leadingelectrical signal wave forms and said engine manifold absolute pressuresignal for producing an ignition dwell signal while the potential levelof each of said leading electrical signal wave forms is greater thanthat of said engine manifold absolute pressure signal; a secondcomparator circuit responsive to said trailing electrical signal waveforms and said engine manifold absolute pressure signal for producing anignition signal when the potential level of each of said trailingelectrical signal wave forms has increased to that of said enginemanifold absolute pressure signal; and circuit means responsive to saiddwell time and ignition signals for completing and interrupting,respectively, an energizing circuit for said primary winding of saidignition coil.